当压力水平逐渐减小，有一点就是结构能够经历足够应力反向之后继续存在来超越组件的预期寿命。

As the stress level is gradually reduced, there comes a point where a structure can survive enough stress reversals to exceed the component's expected life.

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有些人认为硬化的灰铸铁过去曾使零件很容易腐朽老化(因为经过数百万次的应力反向处理后的金属零件最后都会这样)。

Some believe that the hardened gray iron used to make the components simply "fatigues" with age-as metal parts that go through millions of stress reversals eventually do.

youdao

有些人认为硬化的灰铸铁过去曾使零件很容易腐朽老化（因为经过数百万次的应力反向处理后的金属零件最后都会这样）。

Some believe that the hardened gray iron used to make the components simply "fatigues" with age—as metal parts that go through millions of stress reversals eventually do.

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